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The Texas grid recently hit a new winter peak record of about 65,731 megawatts (MW). If Texas' residential heating were 100% electrified, as many climate change mitigation strategies call for, that peak might have been closer to 80,000-90,000 MW, up to about 10,000 more megawatts than we have.

Texas recently joined the rest of the country in experiencing some frigid winter weather. On Tuesday, the high temperatures throughout most of the state didn’t break freezing, setting up Wednesday morning to be one of the coldest daybreaks this decade. Clear skies drove temps down into the teens across most of the state and even sent the Mexican border towns into freezing territory, a rare occurrence indeed.

This doesn’t happen often, but when it does, the result is pretty much the same. Electricity prices within the Texas grid, known as the Electric Reliability Council of Texas, or ERCOT, rise as people try to keep their homes warm when they wake up and get ready for work. In some parts of Texas, wholesale electricity market prices spiked to over $5,000/MW. Quite a jump when you consider average prices are usually in the mid-$20/MWh range.

So why the spike? Most of Texas (and in the South generally) uses electricity for heating. In fact, it’s our preferred heating "fuel." We use electricity to heat our homes and some businesses because these heating systems typically have the lowest upfront costs and we don’t use them that much (we’re a summer peaking state).

Some of these heating systems are direct electric resistance heaters, big coils of wires that heat up when turned on — think of a big toaster in your attic that you blow air through and the air heats up. Some systems are heat pumps, which are basically an air-conditioners running backwards. Heat pumps also use electricity to heat, but are much more efficient than big toasters. However, when the outdoor temperature gets around the low 20s, these systems can’t operate anymore, and therein lies the problem.

So when that rare cold weather strikes and the heat pumps are no longer able to provide heat, their “auxiliary” or “emergency” heat kicks in, and the system reverts to being a big toaster. And if you want to heat a whole house with a toaster, you need a really, really big toaster.

A few numbers.

During the summer, because of Texas’ many air conditioners, residential demand increases about 400% from off peak (~9,000 MW) in the spring to summer peak (~35,000 MW).

While commercial and industrial load only fluctuates about 35% from low to high, ERCOT is built to service all those residential air-conditioners that keep us sane. ERCOT’sall-time peak demand is 71,110 MW, set on Aug. 11, 2016. Most summers see new peaks, but during the Jan. 16-17, 2018, freeze, EROCT hit a new winter peak record of 65,731 MW and blew past the previous winter peak by over 2,800 MW.

A quick back-of-the-envelope thought experiment.

There has recently been a considerable amount of interest in electrifying everything in the U.S. economy. Doing so can make the economy more energy efficient, as well help fight climate change. With that in mind, the National Renewable Energy Lab recently announced the Electrification Futures Study to look at the consequences of a highly electrified US energy sector.

Let’s use this Texas cold snap as a quick case-study. There are 7.4 million households in Texas, with an average home size of about 2000 ft2. We built an energy model and simulated the average Texas home, equipped with a heat pump, and fed it the past few days’ worth of weather data. As expected, the outside temperatures were too cold for the heat pump to operate and the auxiliary heat kicked on. This meant that, during the coldest hours (when ERCOT happened to be peaking and the home’s auxiliary heat was on), the house was drawing over about 2-3 times more power than when the heat pump was operating normally.

If all 7.4 million Texas homes were operating like this, it looks like ERCOT’s peak would have been instead been about 90,000 MW. That is about 20,000 MW more than the summer peak, and about 10,000 MW more generation (depending on how you count) than ERCOT has in its entire system. See my rough calculations here.

In the end, the amount of total energy (MWh) consumed is pretty small because the auxiliary heat might not be on for very long, but the instantaneous power demand (MW) of 'everyone' being on auxiliary heat at the same time is very large. If we want to electrify the home heating space, we need to be honest with what that might mean – lots of generation available for short amounts of time and we will likely need to throw all of our smart grid/Internet of Things/storage(?)/transmission solutions at it. Using higher performance heat pumps and better insulating our homes would help too. It can be done, and to reduce carbon emissions long term, it will probably have to be done, but it is going to take more infrastructure than we have now.

By the way, the weather report has Austin back in the 70s this weekend.

I am a Research Associate in the Webber Energy Group at the University of Texas at Austin and an independent consultant at Ideasmiths LLC. My current research is in the

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I am a Research Associate in the Webber Energy Group at the University of Texas at Austin and an independent consultant at Ideasmiths LLC. My current research is in the area of spatial system-level applications and grid impacts of energy efficiency, resource planning, distributed generation, and energy storage. I am a frequent commentator and keynote speaker on the major energy topics facing our world today. I like mountain biking and enjoy a good cup of coffee.